/*
 * Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package javax.management;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamField;
import java.util.EventObject;

import java.security.AccessController;

import com.sun.jmx.mbeanserver.GetPropertyAction;

/**
 * <p>The Notification class represents a notification emitted by an
 * MBean.  It contains a reference to the source MBean: if the
 * notification has been forwarded through the MBean server, and the
 * original source of the notification was a reference to the emitting
 * MBean object, then the MBean server replaces it by the MBean's
 * ObjectName.  If the listener has registered directly with the
 * MBean, this is either the object name or a direct reference to the
 * MBean.</p>
 *
 * <p>It is strongly recommended that notification senders use the
 * object name rather than a reference to the MBean object as the
 * source.</p>
 *
 * <p>The <b>serialVersionUID</b> of this class is <code>-7516092053498031989L</code>.
 *
 * @since 1.5
 */
@SuppressWarnings("serial")  // serialVersionUID is not constant
public class Notification extends EventObject {

  // Serialization compatibility stuff:
  // Two serial forms are supported in this class. The selected form depends
  // on system property "jmx.serial.form":
  //  - "1.0" for JMX 1.0
  //  - any other value for JMX 1.1 and higher
  //
  // Serial version for old serial form
  private static final long oldSerialVersionUID = 1716977971058914352L;
  //
  // Serial version for new serial form
  private static final long newSerialVersionUID = -7516092053498031989L;
  //
  // Serializable fields in old serial form
  private static final ObjectStreamField[] oldSerialPersistentFields =
      {
          new ObjectStreamField("message", String.class),
          new ObjectStreamField("sequenceNumber", Long.TYPE),
          new ObjectStreamField("source", Object.class),
          new ObjectStreamField("sourceObjectName", ObjectName.class),
          new ObjectStreamField("timeStamp", Long.TYPE),
          new ObjectStreamField("type", String.class),
          new ObjectStreamField("userData", Object.class)
      };
  //
  // Serializable fields in new serial form
  private static final ObjectStreamField[] newSerialPersistentFields =
      {
          new ObjectStreamField("message", String.class),
          new ObjectStreamField("sequenceNumber", Long.TYPE),
          new ObjectStreamField("source", Object.class),
          new ObjectStreamField("timeStamp", Long.TYPE),
          new ObjectStreamField("type", String.class),
          new ObjectStreamField("userData", Object.class)
      };
  //
  // Actual serial version and serial form
  private static final long serialVersionUID;
  /**
   * @serialField type String The notification type. A string expressed in a dot notation similar to
   * Java properties. An example of a notification type is network.alarm.router
   * @serialField sequenceNumber long The notification sequence number. A serial number which
   * identify particular instance of notification in the context of the notification source.
   * @serialField timeStamp long The notification timestamp. Indicating when the notification was
   * generated
   * @serialField userData Object The notification user data. Used for whatever other data the
   * notification source wishes to communicate to its consumers
   * @serialField message String The notification message.
   * @serialField source Object The object on which the notification initially occurred.
   */
  private static final ObjectStreamField[] serialPersistentFields;
  private static boolean compat = false;

  static {
    try {
      GetPropertyAction act = new GetPropertyAction("jmx.serial.form");
      String form = AccessController.doPrivileged(act);
      compat = (form != null && form.equals("1.0"));
    } catch (Exception e) {
      // OK: exception means no compat with 1.0, too bad
    }
    if (compat) {
      serialPersistentFields = oldSerialPersistentFields;
      serialVersionUID = oldSerialVersionUID;
    } else {
      serialPersistentFields = newSerialPersistentFields;
      serialVersionUID = newSerialVersionUID;
    }
  }
  //
  // END Serialization compatibility stuff

  /**
   * @serial The notification type. A string expressed in a dot notation similar to Java properties.
   * An example of a notification type is network.alarm.router
   */
  private String type;

  /**
   * @serial The notification sequence number. A serial number which identify particular instance of
   * notification in the context of the notification source.
   */
  private long sequenceNumber;

  /**
   * @serial The notification timestamp. Indicating when the notification was generated
   */
  private long timeStamp;

  /**
   * @serial The notification user data. Used for whatever other data the notification source wishes
   * to communicate to its consumers
   */
  private Object userData = null;

  /**
   * @serial The notification message.
   */
  private String message = "";

  /**
   * <p>This field hides the {@link EventObject#source} field in the
   * parent class to make it non-transient and therefore part of the
   * serialized form.</p>
   *
   * @serial The object on which the notification initially occurred.
   */
  protected Object source = null;


  /**
   * Creates a Notification object.
   * The notification timeStamp is set to the current date.
   *
   * @param type The notification type.
   * @param source The notification source.
   * @param sequenceNumber The notification sequence number within the source object.
   */
  public Notification(String type, Object source, long sequenceNumber) {
    super(source);
    this.source = source;
    this.type = type;
    this.sequenceNumber = sequenceNumber;
    this.timeStamp = (new java.util.Date()).getTime();
  }

  /**
   * Creates a Notification object.
   * The notification timeStamp is set to the current date.
   *
   * @param type The notification type.
   * @param source The notification source.
   * @param sequenceNumber The notification sequence number within the source object.
   * @param message The detailed message.
   */
  public Notification(String type, Object source, long sequenceNumber, String message) {
    super(source);
    this.source = source;
    this.type = type;
    this.sequenceNumber = sequenceNumber;
    this.timeStamp = (new java.util.Date()).getTime();
    this.message = message;
  }

  /**
   * Creates a Notification object.
   *
   * @param type The notification type.
   * @param source The notification source.
   * @param sequenceNumber The notification sequence number within the source object.
   * @param timeStamp The notification emission date.
   */
  public Notification(String type, Object source, long sequenceNumber, long timeStamp) {
    super(source);
    this.source = source;
    this.type = type;
    this.sequenceNumber = sequenceNumber;
    this.timeStamp = timeStamp;
  }

  /**
   * Creates a Notification object.
   *
   * @param type The notification type.
   * @param source The notification source.
   * @param sequenceNumber The notification sequence number within the source object.
   * @param timeStamp The notification emission date.
   * @param message The detailed message.
   */
  public Notification(String type, Object source, long sequenceNumber, long timeStamp,
      String message) {
    super(source);
    this.source = source;
    this.type = type;
    this.sequenceNumber = sequenceNumber;
    this.timeStamp = timeStamp;
    this.message = message;
  }

  /**
   * Sets the source.
   *
   * @param source the new source for this object.
   * @see EventObject#getSource
   */
  public void setSource(Object source) {
    super.source = source;
    this.source = source;
  }

  /**
   * Get the notification sequence number.
   *
   * @return The notification sequence number within the source object. It's a serial number
   * identifying a particular instance of notification in the context of the notification source.
   * The notification model does not assume that notifications will be received in the same order
   * that they are sent. The sequence number helps listeners to sort received notifications.
   * @see #setSequenceNumber
   */
  public long getSequenceNumber() {
    return sequenceNumber;
  }

  /**
   * Set the notification sequence number.
   *
   * @param sequenceNumber The notification sequence number within the source object. It is a serial
   * number identifying a particular instance of notification in the context of the notification
   * source.
   * @see #getSequenceNumber
   */
  public void setSequenceNumber(long sequenceNumber) {
    this.sequenceNumber = sequenceNumber;
  }

  /**
   * Get the notification type.
   *
   * @return The notification type. It's a string expressed in a dot notation similar to Java
   * properties. It is recommended that the notification type should follow the reverse-domain-name
   * convention used by Java package names.  An example of a notification type is
   * com.example.alarm.router.
   */
  public String getType() {
    return type;
  }

  /**
   * Get the notification timestamp.
   *
   * @return The notification timestamp.
   * @see #setTimeStamp
   */
  public long getTimeStamp() {
    return timeStamp;
  }

  /**
   * Set the notification timestamp.
   *
   * @param timeStamp The notification timestamp. It indicates when the notification was generated.
   * @see #getTimeStamp
   */
  public void setTimeStamp(long timeStamp) {
    this.timeStamp = timeStamp;
  }

  /**
   * Get the notification message.
   *
   * @return The message string of this notification object.
   */
  public String getMessage() {
    return message;
  }

  /**
   * Get the user data.
   *
   * @return The user data object. It is used for whatever data the notification source wishes to
   * communicate to its consumers.
   * @see #setUserData
   */
  public Object getUserData() {
    return userData;
  }

  /**
   * Set the user data.
   *
   * @param userData The user data object. It is used for whatever data the notification source
   * wishes to communicate to its consumers.
   * @see #getUserData
   */
  public void setUserData(Object userData) {

    this.userData = userData;
  }

  /**
   * Returns a String representation of this notification.
   *
   * @return A String representation of this notification.
   */
  @Override
  public String toString() {
    return super.toString() + "[type=" + type + "][message=" + message + "]";
  }

  /**
   * Deserializes a {@link Notification} from an {@link ObjectInputStream}.
   */
  private void readObject(ObjectInputStream in)
      throws IOException, ClassNotFoundException {
    // New serial form ignores extra field "sourceObjectName"
    in.defaultReadObject();
    super.source = source;
  }


  /**
   * Serializes a {@link Notification} to an {@link ObjectOutputStream}.
   */
  private void writeObject(ObjectOutputStream out)
      throws IOException {
    if (compat) {
      // Serializes this instance in the old serial form
      //
      ObjectOutputStream.PutField fields = out.putFields();
      fields.put("type", type);
      fields.put("sequenceNumber", sequenceNumber);
      fields.put("timeStamp", timeStamp);
      fields.put("userData", userData);
      fields.put("message", message);
      fields.put("source", source);
      out.writeFields();
    } else {
      // Serializes this instance in the new serial form
      //
      out.defaultWriteObject();
    }
  }
}
